The present invention relates to an ink liquid supply system for an ink jet system printer of the charge amplitude controlling type and, more particularly, to a constant flow rate pump for use in the ink liquid supply system.
A constant flow rate ink liquid supply pump is highly required in an ink jet system printer of the charge amplitude controlling type to ensure an accurate printing operation. The constant flow rate pump is effective not only to stabilize the ink liquid speed emitted from a nozzle but also to maintain the ink visosity at a fixed value.
A constant flow rate ink liquid supply pump having a plurality of pressure chambers is proposed in our copending application Ser. No. 51,395, "CONSTANT FLOW RATE LIQUID SUPPLY PUMP", filed on June 25, 1979 now U.S. Pat. No. 4,343,596. The constant flow rate pump of U.S. Pat. No. 4,343,596 includes a cam mechanism for converting the rotation of a motor to a reciprocating movement, thereby driving a piston. However, the cam mechanism which is required, complicates the system construction.
To eliminate the disadvantages caused by the cam mechanism, a novel constant flow rate ink liquid supply pump is proposed in copending application Ser. No. 70,639, "CONSTANT FLOW RATE LIQUID SUPPLY PUMP" filed on Aug. 28, 1979 by Masafumi Matsumoto and Matahira Kotani now U.S. Pat. No. 4,278,984, and assigned to the same assignee as the present application, wherein an electromagnetic solenoid is employed to drive the piston. This system is superior to the cam mechanism controlled pump because the piston is driven directly by a plunger associated with the electromagnetic solenoid.
However, the solenoid controlled pump inevitably requires a stopper for determining the stroke length of the piston. The stopper makes contact with the plunger when the plunger is driven in a predetermined direction by a preselected length and noises are created when the plunger contacts the stopper at a high speed. Moreover, the impact will cause a deviation in the preselected stroke length, and the deviation will preclude the desired constant flow rate supply.
Accordingly, an object of the present invention is to provide a compact size plunger pump for use in an ink liquid supply system of an ink jet system printer of the charge amplitude controlling type.
Another object of the present invention is to provide a plunger pump which ensures a constant flow rate liquid supply and creates substantially low noises.
Still another object of the present invention is to provide a novel ink liquid supply system in an ink jet system printer of the charge amplitude controlling type.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a pump integrally includes at least three pressure chambers, which are separated by series connected pistons, which in turn are driven to reciprocate by a plunger associated with an electromagnetic solenoid. The first pressure chamber functions to introduce the ink liquid from an ink liquid reservoir and develop the ink liquid toward a nozzle of the ink jet system printer of the charge amplitude controlling type at a constant flow rate. The second pressure chamber functions to decelerate the movement of the piston, thereby minimizing the impact force which will be created when the plunger contacts a stopper. The third pressure chamber functions to introduce the waste ink liquid collected by a beam gutter of the ink jet system printer and return the waste ink liquid to the ink liquid reservoir.
In a preferred form, the second pressure chamber communicates with the ink liquid reservoir to introduce the ink liquid through a capillary tube conduit. When the piston reciprocates, the ink liquid filled in the second pressure chamber must be decreased or increased through the capillary tube conduit. The resistance at the capillary tube conduit functions to decelerate the piston movement, thereby minimizing the impact force.